U.S. patent application number 13/139539 was filed with the patent office on 2011-10-06 for system of contra-rotating propellers driven by a planetary gear train providing a balanced distribution of torque between the two propellers.
This patent application is currently assigned to SNECMA. Invention is credited to Wouter Balk, Gilles Alain Charier, Francois Gallet.
Application Number | 20110243735 13/139539 |
Document ID | / |
Family ID | 40940557 |
Filed Date | 2011-10-06 |
United States Patent
Application |
20110243735 |
Kind Code |
A1 |
Balk; Wouter ; et
al. |
October 6, 2011 |
SYSTEM OF CONTRA-ROTATING PROPELLERS DRIVEN BY A PLANETARY GEAR
TRAIN PROVIDING A BALANCED DISTRIBUTION OF TORQUE BETWEEN THE TWO
PROPELLERS
Abstract
A system of contra-rotating propellers for an aircraft
turbomachine, including: a free power turbine including a first
rotor; first and second propellers; and a mechanical transmission
system including a planetary gear train fitted with a sun gear
driven by the rotor, at least one planet gear driving the first
propeller, and a ring driving the second propeller. The free power
turbine also includes a second rotor that is contra-rotating
relative to the first rotor, and rotating the ring.
Inventors: |
Balk; Wouter; (Melun,
FR) ; Charier; Gilles Alain; (La Grande Paroisse,
FR) ; Gallet; Francois; (Paris, FR) |
Assignee: |
SNECMA
Paris
FR
|
Family ID: |
40940557 |
Appl. No.: |
13/139539 |
Filed: |
December 17, 2009 |
PCT Filed: |
December 17, 2009 |
PCT NO: |
PCT/EP2009/067446 |
371 Date: |
June 14, 2011 |
Current U.S.
Class: |
416/129 |
Current CPC
Class: |
Y02T 50/66 20130101;
F05D 2260/40311 20130101; F05D 2260/96 20130101; B64C 11/48
20130101; Y02T 50/671 20130101; F02C 7/36 20130101; F02K 3/072
20130101; F02C 3/067 20130101; Y02T 50/60 20130101 |
Class at
Publication: |
416/129 |
International
Class: |
B64C 11/48 20060101
B64C011/48; F16H 1/28 20060101 F16H001/28 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 19, 2008 |
FR |
0858822 |
Claims
1-7. (canceled)
8. A system of contra-rotating propellers for aircraft
turbomachine, comprising: a free power turbine including a first
rotor; a first contra-rotating propeller and a second
contra-rotating propeller configured to be rotated around a
lengthways axis of the propeller system, relative to a stator of
the system; and a mechanical transmission system including a
planetary gear train fitted with a sun gear centered on a
lengthways axis and driven by the first rotor of the free power
turbine, wherein at least one planet gear engages with the sun
gear, wherein one or more planet gear carrier(s) drive(s) the first
propeller, together with a ring engaging with each planet gear and
driving the second propeller, wherein the free power turbine
further includes a second rotor that is contra-rotating relative to
the first rotor, and rotating the ring.
9. A system of contra-rotating propellers according to claim 8,
wherein the first propeller is a downstream propeller, and the
second propeller is an upstream propeller.
10. A system of contra-rotating propellers according to claim 8,
wherein the first rotor of the free power turbine is an internal
rotor, and the second rotor of the free power turbine is an
external rotor.
11. A system of contra-rotating propellers according to claim 8,
wherein the planet gear carrier(s) is/are integral with the first
propeller, and the ring is integral with the second propeller and
the second rotor of the free power turbine.
12. A system of contra-rotating propellers according to claim 8,
wherein the first and second propellers each includes a system of
variable adjustment of their blades.
13. A turbomachine for an aircraft including a system of
contra-rotating propellers according to claim 8.
14. A turbomachine according to claim 13, which is an open rotor
turbomachine.
Description
TECHNICAL FIELD
[0001] The present invention relates, generally, to a system of
contra-rotating propellers, for an aircraft turbomachine.
[0002] The invention also concerns a turbomachine for aircraft
including such a system of contra-rotating propellers.
[0003] The invention preferably applies to aircraft turbomachines,
for example of the jet turbine or turboprop engine type. It applies
more particularly to turbomachines called "open rotor"
turbomachines, within which a free power turbine drives both
contra-rotating propellers, directly or indirectly through a
mechanical transmission system forming a reduction gear and notably
including a planetary gear train. In these systems of
contra-rotating propellers, the propellers therefore have no
fairing at their outer radial ends.
STATE OF THE PRIOR ART
[0004] From the prior art, turbomachines with systems of
contra-rotating propellers are indeed known, the propellers of
which are driven by a mechanical transmission system, habitually
taking the form of a differential reduction gear. This differential
reduction gear includes a particular planetary gear train, the sun
gear of which is rotated by a rotor of a free power turbine, the
planet gear carrier of which drives the first propeller, and the
ring of which drives the second propeller. With this regard, it is
noted that depending on the position of the contra-rotating
propellers relative to the free power turbine which is driving
them, the first propeller constitutes the downstream propeller and
the second propeller the upstream propeller, or vice versa. Be that
as it may, unlike a single planetary gear train, the ring is not
fixed, but mobile.
[0005] With such a planetary gear train, the two propellers cannot
be subject to the same aerodynamic torques. The mechanical
balancing equations of the satellites show that these two torques
necessarily have a constant ratio, depending on the geometrical
characteristics of the reduction gear. This ratio is necessarily
other than a ratio of equality. Indeed, the ratio between the
torque C1 applied to the first propeller and the torque C2 applied
to the second propeller is expressed as follows:
C1/C2=(R+1)/(R-1);
[0006] where R is the reduction ratio defined by the planetary gear
train.
[0007] Thus, in order to attain a ratio of torques which is close
to equality, it is necessary to increase the reduction ratio R
which, however, for questions of mechanical feasibility, cannot be
greater than 10. In addition, the increase of the reduction ratio R
inevitably leads to an increase of the overall mass of the
propeller system, having an adverse effect on the turbomachine.
[0008] As a consequence of the unequal ratio between the torques,
one of the two propellers will generate a greater gyration of the
secondary flow than the other propeller, causing a residual
gyration of the output flow, appreciably limiting the propulsion
efficiency and increasing deleteriously the acoustic level of the
turbomachine. In reality, it is the first propeller driven by the
planet gear carrier which always has a greater load in terms of
torque.
[0009] Moreover, this difference between the two torques also
generates an increased stress of the means used for mounting the
turbomachine on the aircraft, and these means must accordingly be
over-dimensioned to support the extra load which is applied to
them.
SUMMARY OF THE INVENTION
[0010] The purpose of the invention is therefore to provide at
least partially a solution to the disadvantages mentioned above,
compared with the embodiments of the prior art.
[0011] To accomplish this, the first object of the invention is a
system of contra-rotating propellers for aircraft turbomachine,
including: [0012] a free power turbine including a first rotor;
[0013] a first contra-rotating propeller and a second
contra-rotating propeller intended to be rotated around a
lengthways axis of the propeller system, relative to a stator of
this system; and [0014] a mechanical transmission system including
a planetary gear train fitted with a sun gear centred on the said
lengthways axis and driven by the said first rotor of the free
power turbine, where at least one planet gear engages with the said
sun gear, where one or more planet gear carrier(s) drive(s) the
said first propeller, together with a ring engaging with each
planet gear and driving the said second propeller.
[0015] According to the invention, the said free power turbine also
includes a second rotor which is contra-rotating relative to the
said first rotor, and rotating the said ring.
[0016] The invention therefore advantageously seeks to address the
torque deficit received by the second propeller by acting such that
the latter is partly driven by the second rotor of the free power
turbine, via the ring of the planetary gear train. In other words,
the torque transmitted to the second propeller by the ring no
longer originates solely from the satellites as was previously the
case, but also originates from the second rotor of the power
turbine, which therefore takes on a contra-rotating character.
[0017] This feature leads to a balance of the two torques
transmitted respectively to the two propellers, and the ratio
between these two torques is effectively equality. The consequence
is, firstly, that both propellers will each generate a roughly
identical gyration of the secondary flow, which prevents the
deleterious appearance of a residual gyration of the output flow.
Thus, the aerodynamic flow is satisfactorily rectified at the
output from the propeller system, which procures an improved
propulsion efficiency and a reduction of the acoustic level
produced.
[0018] Furthermore, as a consequence of this balancing of the
torques, the means used for mounting the turbomachine on the
aircraft are subject to less mechanical stress, and can
consequently be of a less costly design in terms of encumbrance and
mass.
[0019] Moreover, within the contra-rotating free power turbine, the
first rotor can rotate less rapidly than in the case of a
traditional turbine, whilst preserving the same power delivered at
the output of this turbine. This reduction of the rotational speed
of the first rotor not only allows its design to be facilitated and
simplified, since the centrifugal forces applied to it are lesser,
but also enables the reduction ratio conferred by the planetary
gear train to be reduced, since the speed of its sun gear, driven
by the first rotor, is lower. A substantial gain in terms of mass
obviously results from these two advantages.
[0020] Moreover, it should be noted that a reduction gear is
characterised by mechanical efficiency, implying that a part of the
transmitted power is transformed into heat. Given the power of
several megawatts supplied by the aircraft turbomachine, this heat
is very substantial. These calories are habitually evacuated by
means of an oil circuit, and an air-oil exchanger. The installation
of this exchanger in the nacelle constitutes a major constraint for
the integration of the propulsive assembly, due to its encumbrance,
mass and drag. With the planetary gear train implemented according
to the invention, part of the power no longer transits through the
reduction gear, but is transmitted directly to the second
propeller. Consequently, the quantity of calories to be dissipated
in the exchanger is lesser, such that the latter can be of smaller
dimensions. This therefore has a beneficial effect for the mass,
encumbrance and drag of the air-oil exchanger.
[0021] The invention is applicable to all turbomachines, and
particularly those known as "open rotor" turbomachines. In the
latter case the invention applies whether the propeller system is
positioned upstream or downstream from the gas generator. In both
these cases, within the propeller system, it can be envisaged to
position the power turbine upstream or downstream from the
contra-rotating propellers. This is also applicable for the
position of the planetary gear train with regard to the
propellers.
[0022] The said first propeller is preferably the downstream
propeller, and the said second propeller is the upstream propeller.
This specific arrangement is chosen particularly when the propeller
system is positioned downstream from the turbomachine's gas
generator, i.e. when the turbomachine is of a design producing a
propulsion known as a "pusher" design. Naturally, a reverse design
could be envisaged, in which the said first propeller would be the
upstream propeller, and the said second propeller would be the
downstream propeller, without going beyond the scope of the
invention. This other solution is chosen particularly when the
propeller system is positioned upstream from the turbomachine's gas
generator, i.e. when the turbomachine is of a design producing a
propulsion known as a "puller" design.
[0023] Whatever the envisaged design among those mentioned above, a
choice is preferably made such that the said first rotor of the
free power turbine, driving the sun gear, is the internal rotor,
and the said second rotor of the free power turbine, driving the
ring, is the external rotor, although a reverse design could be
envisaged, without going beyond the scope of the present
invention.
[0024] The said planet gear carrier(s) is preferably integral with
the said first propeller, and the said ring is integral with the
said second propeller and the said second rotor of the free power
turbine.
[0025] The first and second propellers preferably each have a
system for variable adjustment of their blades. In a known manner,
these systems are controlled such that the speed of rotation of
both propellers is kept roughly constant in operation, whatever the
engine speed.
[0026] Another object of the invention is a turbomachine for
aircraft including a system of contra-rotating propellers as
described above, where this turbomachine is, for example, a
turboprop engine, but can alternatively be a turbojet with
contra-rotating fan. Naturally, in the latter case, the
above-mentioned mechanical transmission device is intended to move
the contra-rotating fan of the turbojet. As mentioned above, the
invention preferably applies more particularly to turbomachines
called "open rotor" turbomachines, within which a free power
turbine drives both contra-rotating propellers, indirectly through
a mechanical transmission system forming a reduction gear and
notably including a planetary gear train.
[0027] Other advantages and characteristics of the invention will
appear in the non-restrictive detailed disclosure below.
BRIEF DESCRIPTION OF THE ILLUSTRATIONS
[0028] This description will be made with reference to the attached
illustrations, among which
[0029] FIG. 1 represents a schematic lengthways half-section view
of a turbomachine for aircraft, according to a preferred embodiment
of the present invention;
[0030] FIG. 2 represents an enlarged view of the system of
contra-rotating propellers fitted to the turbomachine shown in FIG.
1; and
[0031] FIG. 3 represents a section view taken along line III-III of
FIG. 2.
DETAILED ACCOUNT OF PREFERRED EMBODIMENTS
[0032] With reference to FIG. 1, a turbomachine 1 of the "open
rotor" type according to a preferred embodiment of the present
invention can be seen.
[0033] In the figures, direction A is the lengthways direction or
axial direction, parallel to lengthways axis 2 of the turbomachine.
Direction B, for its part, is the radial direction of the
turbomachine. In addition, arrow 4 shows the direction of motion of
the aircraft under the action of the thrust of turbomachine 1,
where this motion direction is contrary to the principal outflow
direction of the gases within the turbomachine. The terms
"forward", "upstream", "aft" and "downstream" used in the remainder
of the description should be considered as relative to the said
direction of motion 4.
[0034] In the forward part, the turbomachine has an air intake 6
which continues towards the rear through a nacelle 8, where the
latter globally includes an external skin 10 and an internal skin
12, both the latter being centred on axis 2 and offset radially one
from the other.
[0035] The internal skin 12 forms an external radial casing for a
gas generator 14, including the traditionally, from forward to aft,
a low-pressure compressor 16, a high-pressure compressor 18, a
combustion chamber 20, a high-pressure turbine 22 and an
intermediate-pressure turbine 24. Compressor 16 and turbine 24 are
connected mechanically by a shaft 26, thus forming a low-pressure
body, whereas the compressor 18 and the turbine 22 are connected
mechanically by the shaft 28, forming a body of higher pressure.
Consequently, the gas generator 14 is preferably of traditional
design, called a two-spool design.
[0036] Downstream from the intermediate-pressure turbine 24 is a
system of contra-rotating propellers 30, forming the receiver of
the turbomachine.
[0037] This system 30 includes a free power turbine 32, forming a
low-pressure turbine, and which has the feature that it is
contra-rotating. Indeed, with reference more specifically to FIG.
2, it includes a first rotor 32a constituting the internal rotor of
the contra-rotating turbine, and a second rotor 32b constituting
the external rotor of this turbine, where this second rotor 32b is
also called the external drum.
[0038] The system of propellers 30 includes a stator or casing 34,
centred on the lengthways axis 2 of the system, and notably
enclosing the said free power turbine 32. This stator 34 is, in a
known manner, intended to be integral with the other casings of the
turbomachine. In this regard, it is recommended that the system of
propellers 30 is preferably designed such that the propellers have
no external radial fairing surrounding them, as is visible in the
figures.
[0039] In addition, downstream from the contra-rotating turbine 32
the propeller system 30 includes a first propeller 7 or downstream
propeller, supporting blades 7a. In analogous fashion, the system
30 includes a second propeller 9 or upstream propeller, supporting
blades 9a. Thus, the propellers 7 and 9 are offset relative to one
another in direction 4, and both are located downstream from the
free turbine 32.
[0040] Both propellers 7 and 9 are intended to rotate in opposite
directions around axis 2 on which they are centred, and the
rotations occur relative to the stator 34, which remains
immobile.
[0041] For the rotational drive of these two propellers 7 and 9, a
mechanical transmission system 13, forming a reduction gear and
notably including a planetary gear train 15 is used.
[0042] With reference to FIGS. 2 and 3, the drive 15 is fitted with
a sun gear 17 centred on the lengthways axis 2, and supported by a
sun gear shaft 19 having the same axis, and coupled securely
upstream with the first rotor 32a, by means of a flange 38. Thus,
rotor 32a directly rotates the sun gear 17, the latter taking the
form of an externally toothed wheel.
[0043] The drive 15 also includes a planet gear 21, and preferably
several of these, as is visible in FIG. 3, where each of them
engages with the sun gear 17. Each planet gear 21 is supported by a
planet gear shaft 23 with an axis which is eccentric relative to
axis 2, and which takes the form of an externally toothed
wheel.
[0044] In addition, drive 15 is fitted with a planet gear carrier
25 centred on the lengthways axis 2, and supporting rotationally
each of the satellites 21, through the shafts 23, respectively. The
planet gear carrier 25 is supported by a planet gear carrier shaft
29 having the same axis, which is integral with the first propeller
7, as is visible in FIG. 2, such that it is able to rotate it
directly.
[0045] Lastly, drive 15 has a ring 31 centred on the axis 2 and
supported by a ring shaft 33 of the same axis, and this ring 31
engages with each planet gear 21. Shaft 33 extends downstream and
is integral with the second propeller 9, such that it is able to
rotate it directly. For example, this shaft 33 is located around
the shaft of the planet gear carrier 29 with which it is
concentric, as shown in the figures.
[0046] The ring 31, taking the form of an internally toothed wheel,
has the additional feature that it is supported by another ring
shaft 35, having the same axis, and extending, for its part, in an
upstream direction. This ring shaft 35, positioned around the sun
gear shaft 19 with which it is concentric, is coupled securely with
the second rotor 32b by means of a flange 40. Thus, rotor 32b also
participates directly in the driving of the ring 31, and therefore
in the driving of the upstream propeller 9. This enables a ratio of
equality to be obtained between the torques transmitted
respectively to the downstream propeller 7 and to the upstream
propeller 9, so as to obtain an improved efficiency of the
turbomachine.
[0047] Finally, it should be noted that in this preferred
embodiment, in which each propeller is fitted with a system for
variable adjustment of its blades, the planetary gear train 15 is
positioned perpendicular to and within a casing 42 separating the
contra-rotating free power turbine 32 and the propellers 7, 9. This
casing 42, also called the exhaust casing, or again the "static
frame", supports an engine attachment 44 intended to allow the
turbomachine to be mounted on to the structure of the aircraft.
[0048] Naturally, various modifications can be made by the skilled
man in the art to the invention which has just been described,
solely as non-restrictive examples.
* * * * *